Duplex balance indicator



Jul 10, 1945.

A. F. CONNERY DUPLEX BALANCE INDICATOR Filed July 10, 1945 la r-MH lNL\NE FRETURN LINE 0R GRQUND INVENTOR Alder F Connery ATTORNEYSarti'oularly toma method I of indicatdition for balance; as between] thehm sy en kn weev simultaneously, in, both "direcances' the real lineextending: between eta:

sthroligh' another portion to the; artificial fe t fi in i ir lii isfihH lfiQW 3 1 1 by 'both 'l'oo i tiohs ldf the transmitted sign lcurrehtibut in, Opposite directionsso that when the artificiallineifbalarices the real 1 line the effects offth'e' transmitted signalare balanced out and It is c m n practice toperiodioallybstoptransmission on a dupleig telegraph line 1 and to balance theflsystenduring the period or; stoppage Qf hearse, this istwasteful of; linetime,

I furthermore there is no assurance-that k i ll ltt la iI Q Fz F exi t nb tw P r if: balanoingsoi the circuit. 'I'his unbalanc e 1 besii'fficient to interfere with thejreception ig'nals nd jthus. of itselfcauses waste of tim" Furthermoregduring periods of varying weather-I(conditions over the line the fred l n Wh wl ee ust balanced "is an oectof the presentinventio n to make ossible to procure an indication ofthe con-- ditionbf the 1mg, 11 respect to balance while the telegraphcircuit is in operation. I l 1, i anothert obiectuof the inVentiQnt Dville; equip jlfinfi; f0r giving such an indication whichgnotl only.indicates whether or not the line isinlha ance, but it "unbalancedwhether ithe unbalanc is caused byutoo much oritoo little iesistanceunthe artificial line I 1 It:isxanfurther object "of i theinvention {to provide la -:methoclof .indicatingunbalance "which cansbeiperformed with the use of very little equipment and without th dangerof interruption:tofthehormal transmission. i

will appear when the*followingspecification is considers onnectionjwiththe annexed "drawthere is*shown a" scheniatic fiia male whic thisarrangement the:transrnitted pllt into two parts; 'onewof whichpassestm-ougn ajportion of the receiving cir ciiitto he maihilinean dthe other-Moi which fgnal only; is effective itol actuate grain of. oneteri ninal the I duh x f l i with one of Systhm" 1 t Referring now tothe drawmgtthe resistances H1 and I lfare'resistances in the two legs ofthe duplex circuit and are joined at the b which is therefore; the pointcornmonlyhnown as the fsplit" of the duplex. It will be understood that.in abridge typeduplexthe resistanees l and 'liY willeach be in serieswith onej of the bridge arms while ma differential w the resistances ID-and l the windings orthe differ n 1 ceiving relayi a The obpositeen dsoffthel resistances I01, and I ar connected respectively tothefrhainfline and to the; artificial line in th usualh anrler. Themainfline, of (19112156, e tends to t eij j pt; line is connected 'therstation a d the artificial to a metallic'returnor to ground. "T hem iseffected by applying either positi w Referring iagain tothe drawingclearft halt if there alan d artificial linefbare in balance and theresistances t0 an i] equal,

then the transmitted currents, through resist ances Ill and H willbeeqiial; Futher moreythe voltage from point 12 to point [It be lequalto the voltage between points I 2 and All and the voltage betweenpointsfl8 and 20 will rbefzero.

onthe resistancesl fl andil l willbe zero. "The i voltage between pointsFl and. 20 will be-un equal. Iffa pointf23 is selected;electricalljasdistant from point 22as isgpointlllsthen the resistance fror'nboint 12x0point '2; s jequalto i be equalbutopposite in sign tlo that} A- Qthei'objeCtQand jfeatures of the invention 1 It will also be clear that thevoltage between i any two similar points suchas pointsitand 122 theresistanee between points 22 and 20, More over, the "voltage betweenpoints 121: and 20 :fwill WW? points 2! Land'23.

- If we now suppose thatthe resiSfianeofthe artificial lineis nolonger-equal to buttis larger th h -o h in ne than itFW 1 eer i that thevoltage ifrom point lzitd e nt 18 will i t be greater than the voltagefrom point l2 to point 2o, and the Voltage from point I2 to point 2t maybe greater than, equal to, or less than that trom point 123m point at. 3Thus the voltage between i points 2| and 20 may beless than itwaswiththe artificial line balanced,finajr bejzero ,or maybe greater 'thanbefore, but; if the latter is the case, 3 e11 ioppqsite polarity!) nHowever,v :unless the ,artie flcialfline resistance isiried innmte, thevoltage H iQI ie'gQLt iV" battery from the batteries l3 andl'ALthroughthe limitingreslistances l5 and between points 2| and 20 mustbe less than the voltage between 2| and .23 which will always increasewith an increase in the artificial line reequals that from point 2| topoint 20, although opposite in sign.) Thevoltage from point 2| to point23 exists because the voltage from point l2 to point 23 is smaller thanthat from point |2 to point 2 I. Therefore, as the resistance of theartiL-J ficial line is increased, thus reducing, the voltage from pointI2 to point 20, the voltage from point" I2 to point 23 becomessmalleranrtsince.the:;volt-. i age from point l2 to point 2|.rema-insconstant; the voltage from 2| to 23 will-rise by exa'ctl-y the amount ofthe reduction from, l2. to. 23.. On the voltage. from l2 to 20 is largerthan the. voltage I2 to 2|. Thus as, the artificial line resistance isincreased andthe voltage from I2 to 20 decreased, the voltage from 2| to20 will first decrease to zero (which will occur when the voltage |2 to20 is equal to the voltage l2 to 2 l and will'then' again increase;but'will then be of oppositesign, It will be seen that once the voltageoccurring-between points 2| and 20'has passed through zero'it'willbeequal'to the voltage between points 2| and 23 minus the voltagebetween'p'oints 23 and 2H.

Thus it follows that with the artificial line resistance higher thanthat for balance thevoltage from point 2| to point. 23 will always begreater than that from point 2 I to point 20. I

[Bythe same reasoningit follows that if the artificial line resistanceis less than that required for balance the voltage from point2| to point2ll will always be greater than that from point 2|"topoint23.'Any'voltage' developed between points |2"and 2 tby theincoming signalwill add algebraically to a the voltages between points; 2| and 23 andthose between points. 2| and 201 Since the voltages between points; 2|and 20 and points 2| and 23,may 1 be, and in actual practice where theartificial line unbalance is never allowed to become. great, are

of opposite polarity, there will be an addition in one case andsubtraction, in the other. Upon the reversal of? either the. incoming orthe transmitted signal one. set of signs will reverse and the 'voltagesbefore added are now of opposite sign and are. subtractive and" viceversa.

' To illustrate the foregoing, let. us assume that the artificiallineresista'nce'is too. high, and that positive battery. is supplied tothe key ll of. the transmitter (this may, of course, be the tongue of atransmitting relay) Then let usassumefthat the'voltage from point 2| topoint23 is. three. volts with positive. at point 23, and the voltagefrom point 2I- to point'20, two'voltswith. negativeat 20. If we add tothese voltages an incoming signal voltage betweenv points l2 andZ'lioifiize volts with positive at" point '12 we then find" that thevoltage between points 2| "and arenas. eight volts andthatbetween'jpoints 2| 21) three volts; It now the transmittingkey 1 .tpemtato its other contact. and applies. negative polarity to thesplit I2 ofthe duplex, the voltagesbetween points 21 and 23'and points 2| andZU dueto the transmitted-current will'be of the same magnitudeas before butopposite in. sign.' Therefore, with the received current the sameasbeforelfthe total voltage" differencejbetweenpoints, 2 .iand 2.3willfnow be two voitsai idthat between points; 2|

and 20 seven volts. Therefore, it is clear that with the artificial lineresistance too great there will always be existing as the circuitoperates higher voltages between points 2| and 23 than between points 2|and 2|]. Similarly, if the artificial line resistance is too low thegreater voltage will always occur between points 2| and 20, while if theartificial line resistance is proper the maximum voltages occurringbetween. 21 and 23 and between 2| and 20 will b equal.

Therefore, all that is necessary to -determine the condition of theartificial line is to provide somemeans of indicating whether themaximum voltage between points 2| and 20 is greater than, equal to,; or:less than that between points 2| and -123. If: this-:is done: withoutdisturbing the operation. of the circuit; then rebalancing may becarried onwhile the. telegraph circuit is in operation.

While there' are many methods of determining therelationship between thepeak voltages occurringbetween. points 2| and 23 and 2| and20, one ofthe simplest i illustrated in the drawing in order to fully illustratethe methods The intwo neon lamps 24 and 25. One electrode ofeach of theslamps is connected by means of aconductor 26 and limiting resistor 33 toa. potentiometer 21 which supplies a biasing voltage to theselamps. Alea-(i 28 is provided whichimaybe connected to the tap" point 2| of theresistance I0 and adjusted upon the potentiometer '21 to supply theproper voltage to la'mps 24 and The battery-29 supplying-thebiasing-voltage may be poled as shown or reversely since theadjustmentof the potentiometer willhave the same effect in either case. Theotherelectrodeoi lamp 25 is connected to metal) point 20 of resistance Handthe second electrode of lamp 24 isin like manner connected to the tappoint 23 of resistance However; the lamp 2 1 isconnectedto point 23through the biasing potentiometer 30 in order that the lamps may beadjusted so that they will fire at the same voltage level.

In using the device the procedure isas follows; With theindicatingcircuit comprisingthe el'e-' rnents just above describeddisconnected'fromthe telegraph circuit and the leads 28, 3| and 32connected together, the bias voltage supplied by the potentiometer 21 isincreased until either lamp-24- or lamp 25 ignites. If lamp 2'4 ignitesthen the voltage supplied by the potentiometer Wis made more negativewhile if 25 ignites it is made morepositive: Potentiometer'fl is againadjusted to causethe lighted lamp to be extinguished. This procedure isrepeated untilupon increasing the voltage-supplied bypotentiometerZI-bothl'amps-Iight at-the same' ti'nie'. Wherrthis is achieved the set'isin balance-and ready for use. a

Thereuponthe connections indicated? in i the drawing are; made, that is.conductor-'28 is connectedltovtap point;2|:, conductor: 3 topoin-t- 23and xconductdr-SS: to: point 202 The-adjustment of; potentiometer: 21is; first setitomake the voltage it supplies a.minimum,.therebypreventingeither lamp from lighting'since' thez'signai voltages: in thecircuit alone; arenot encugh ..tc-; cause ignition. Then; adjustmentslowly. made: on

lamps begins to ,,If the artificial line. re-.

sistanceis set too low,;1amp25-whicha is marked low will fiash'.Thereupon the; artificial line resistanceisv increased by. somesuitableflaluajqr 1.5, example. 50. ohms, Ifthis; causes the low lampdicating device shown in the drawing comprises the potentiometer 21until: one or: bothv-ofi-the '25 to cease flashing and the high lamp 24to begin, the proper value artificial line resistance for balance issomewher between the old and new values and is so set. If, however, uponadding the50 ohm increment both lamps begin to flash this setting of theartificial line is the propof flash to the optimum and confine the fiashto one lamp as much as is possible.

Although one method of indicating whether the peak voltage occursbetween points 2| and 23 or points 2| and has been described, it is tobe understood that this is for the purposes of illustration only andthat many other methods might be utilized.

What is claimed is:

l. The method of determining the condition of balance between the realand artificial lines of 'a duplex telegraph system during operationthereof, which comprises comparing the peak voltage appearing between anarbitrary point on a resistor in the real line leg of the duplex and i apoint electrically removed a predetermined distance in one directionfrom the analogous point on a resistor in the artificial line leg of thduplex, with the peak voltage appearing between the said arbitrary pointon the resistor in said real line leg and a point electrically removed.

the predetermined distance in the opposite direction from the analogouspoint on the said resistor in the artificial line leg of the duplex.

2. The method of determining the condition of balance between the realand artificial lines of a duplex telegraph system during operatingthereof, which comprises comparing the maximum voltage appearing betweenthe junction of a resistor in the artificial line leg and the artificialline and a point on a resistor in the real line leg electrically removeda predetermined distance from the junction of the said resistor with thereal line, with the maximum voltage appearing between this second pointand a point on the first mentioned resistor electrically removed fromthe junction .of the said sistances and the real line 1 balanced, and inwhich direction.

3. The method of claim 2, characterized in that said predetermineddistance is less than half of the length of the said real line resistor.

4. The method of claim 2 further characterized in that the saidartificial and real line resistors are equal and the predetermineddistance is less than half the length of the saidreal line resistor;

5. The method of determining the condition cf balance between the realand artificial lines of a duplex telegraph system during operationthereof, which comprises applying balanced peak voltage indicatingcircuits across points in the legs of the duplex circuit, saidindicating circuits being biased to cut off, the points across whichsaid indicating circuits are applied being such that one of the twoindicators is under control of the voltage from a tap point on aresistor in the real line leg located a predetermined distance from thejunction of the resistor and the line, and a point on the artificialline leg located twice the said predetermined distance from the junctionof the resistor and the artificialfiline, and the second of the twoindicators is under control of the voltage existing between the said tappoint on the real line leg resistor and the junction point between theartificial line leg resistor and the artificial line, and increasing thebias until one'or both of the indicators operates, thereby indicating ifboth indicators'operate that the artificial and real lines are balancedand if one indicator only operates that the line is un- 6. A device fordetermininga condition of balance and unbalance between the real andarti ficial lines of a duplex telegraph system during operation thereof,comprising in combination, a resistor in each leg of the duplex, a firsttap on the resistor of the real line leg of the duplex at aIpredetermined distance from the junction of the line with saidresistor, a second tap on the resistor in the artificial line leg of theduplex located at a point twice the said predetermined distance from thejunction of the artificial line with the said resistor, a third tap atthe point tap to the thirdtap, and means to gradually change the biasapplied to said indicating circuits whereby said indicating devices willindicate when the real and artificial lines are in balance.

' ALDER F. CONNERY.

